Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 230746 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 346 AM EDT Tue May 23 2017 .SYNOPSIS...
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High pressure will build into the northeast U.S. today with fair weather and moderating temperatures in the upper 60s to lower 70s. A few afternoon showers are possible Wednesday, but high temperatures will continue to warm into the low to mid 70s. On Thursday low pressure will move out of the Tennessee and Ohio Valleys and will bring widespread rainfall across the North Country on Thursday and Friday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 340 AM EDT Tuesday...Winds have eased as surface high pressure builds across the forecast area. Partial clearing overnight as drier air works downward from the mid levels. The 500 mb ridge shifts east during the near term period as the low to the west deepens. Great Lakes 500 mb low gets kicked out and moves across southern Quebec in the northern stream today, bringing a few clouds along the border during the day. Weak westerly flow and a little sun will allow temperatures to warm into the 60s to low 70s. Ridging continues tonight, and low level moisture trapped under inversion, wet ground from recent rainfall and light winds will contribute to valley fog formation. A 500 mb shortwave trough moves out of the base of the mean trough to our west, and up the Atlantic coast. A surface low spins up along the coast, and the main precip area with this feature will brush southern New England tonight, with no precip over Vermont/northern NY. Lows tonight in the 40s to low 50s.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
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As of 340 AM EDT Tuesday...For Wednesday the northeast is under the influence of a weakening surface ridge, while a weak mid level vort max lifts northeast. Combination of a little bit of lift from this feature and some differential heating over the mountains break out slight to low chance pops during the day in the northern Adirondacks and part of the Green Mountains. Warming trend continues into Wednesday with highs generally in the 70s, and lows Wednesday night in the 50s. Changes start on Thursday as the low to the west begins its move to the east. Surface and upper low remain further to south/southwest with diffluent flow aloft. 300 mb southerly jet noses into New York/Vermont during the day Thursday, while 850 mb easterly flow brings Atlantic moisture into the area. Pops begin to increase far western St. Lawrence County before sunrise, then continue to increase west to east during the day. Temperatures Thursday 5-10 degrees cooler than Wednesday with rain, clouds, and cool flow off the Atlantic.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 259 AM EDT Tuesday...New 00z guidance showing some disagreement with evolution of closed mid/upper level trof and associated surface low pres. GFS shows a track further east with limited qpf Thursday Night into Friday...while ECMWF shows a negatively tilted and vertically stacked system moving from the Mid Atlantic into Southern New England during this time period. Both agree on precip across our cwa...but exact details on placement of heaviest precip axis and associated pops still has some disagreement. Will continue to mention high likely to low cat pops for Thursday Night into Friday (65 to 80%)...with highest values central/eastern cwa. Expecting a similar type scenario for qpf...as nose of easterly 925mb to 700mb jet is angled toward our eastern zones...helping to enhance moisture advection off the Atlantic. Speaking of Atlantic...expecting a chilly maritime airmass over our cwa during this time period and have cut superblend temps by 2 to 4 degrees...especially eastern/central cwa. The combination of cooler easterly flow...lots of clouds/precip...and progged 925mb temps btwn 6-8c support highs mid 50s to mid 60s. Warmest temps will be western dacks/SLV. For the weekend...weak 1013mb high pres builds into the North Country for Saturday...with still some embedded short wave energy and moisture with westerly flow aloft impacting our northern zones. The combination of lingering moisture...upslope flow...and weak energy aloft...cannot rule out a few midday showers...especially central/northern cwa on Saturday. 925mb to 850mb thermal profiles support highs very close to normal with mid 60s to mid 70s depending upon elevation and cloud coverage. For Sunday...still some uncertainty on placement of weak backdoor cold front or developing warm front lifting from southwest to northeast across our region. This weak convergence with embedded energy aloft may provide enough lift to support a few afternoon showers. Instability is limited and displaced to our southwest...so not anticipating any thunder threat. Have continued to mention slight chance to chance pops...with threat increasing during the afternoon hours. In addition to precip uncertainty...still some question on max temps for Sunday...with a wide range in thermal profiles. We will stick close to superblend values...which is consistent with previous couple of forecasts. Highs mainly in the upper 60s to mid 70s...with 74 expected at BTV. Even more uncertainty as we head into early next week...associated with additional energy aloft and timing of another surface cold front. Latest ECMWF shows several boundaries lifting across our region with numerous embedded vorts in the flow aloft...along with ribbons of enhanced mid level moisture. Initially instability is limited...but increases some on Tuesday to support a chance of thunder. Will continue to mention chance pops with near normal temps...as we have plenty of time to work out the details in the upcoming days. Bottom line not expecting any long windows without the chance for rain and no significant heat in days 4 thru 7. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... Through 00Z Wednesday...A challenging aviation forecast continues thru 12z this morning with fog product and obs showing multi cloud layers with categories ranging from ifr at rut/mpv to vfr elsewhere. Thinking ifr conditions become mvfr/vfr at rut/mpv shortly as winds help with mixing. The combination of yesterdays rainfall and lighter winds after 08z...and several locations going 3 to 6 degrees below cross over temps...thinking some fog/br will develop between 08z-11z. Have utilized tempo group at rut/mpv and slk to highlight fog/br potential early this morning. Overall confidence in IFR potential is on the low side...given 10 to 15 knots of winds around 975mb. After 12z...expecting cigs/vis to become VFR with winds shifting to the north at 4 to 8 knots...with some localized terrain driven gusts. Some high clouds possible today as coastal system passes to our east. Outlook... Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. Breezy. Likely RA. Thursday Night: MVFR with areas of IFR CIGS MPV. Breezy. Likely RA. Friday: MVFR with IFR MPV/SLK. Likely RA. Friday Night: VFR. Chance SHRA. Saturday: VFR. Slight Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Hanson NEAR TERM...Hanson SHORT TERM...Hanson LONG TERM...Taber AVIATION...Taber

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